math

If painter A can paint a room in three hours by themselves, and painter B can paint the same room in four hours, and painter C can paint the same room in six hours, how long will it take for all three to paint the room together if they do not get in each others way? Thanks

A painter can paint a racquetball court in 8 hours. His assistant needs an additional 2 hours to paint the same court working by himself. How long will it take both of them working together to paint the court.

Painters A and B take 3 hours to paint a room Painters B and C take 5 hours to paint the same room Painters A and C take 7 hours to paint the same room How long would it take all three to paint the same room?